Two-piece cans are by far the most common type of metal containers used in the beer and beverage industry. They are usually formed of aluminum or tin-plated steel. The two-piece can consists of a first cylindrical can body portion having an integral bottom end wall and a second, separately-formed, top end panel portion which, after the can has been filled, is double-seamed thereon to close the open upper end of the container.
The can body is formed in a body making apparatus which draws and irons a metal blank (sometimes a preformed cup) into a deep, cylindrical cup. In a first step, the metal blank is fed into the apparatus, and a metal cup is formed in a drawing process. The cup typically has a sidewall diameter that is generally equal to the sidewall diameter of a finished can body. The sidewall at this point is generally unchanged from a sidewall of the metal blank and does not have a finished height. Additionally, the sidewall at this point has a thickness greater than that of a finished can body. In subsequent steps, the drawn cup is passed through ironing tools. These tools lengthen the cup sidewall without changing the diameter of the cylindrical sidewall. The metal needed to lengthen the sidewall comes from the thickness of the sidewall. Accordingly, as the cup passes through the ironing tools, a height of the cylindrical sidewall becomes greater (it is lengthened) and the thickness of the sidewall is decreased. In a final step, the bottom of the cup is shaped by a forming tool. The resultant unfinished can body has a cylindrical sidewall and a domed bottom profile. In a subsequent manufacturing step, the upper portion of the sidewall is necked in so that a reduced diameter neck is formed.
FIG. 1 shows a typical existing body making apparatus 10 which carries out the process described above. The apparatus 10 is centered about a longitudinal axis 50. A ram 14 and punch assembly 15 (collectively referred to herein as the ram) is axially aligned with the longitudinal axis and is generally adapted, as in sized and shaped, to pass through a central cavity 16 of the apparatus 10. The cavity 16 is at least partially formed by a plurality of annular tools, each having an aperture substantially axially aligned with the longitudinal axis 50.
A redraw sleeve 18 is positioned to the right of the ram 14 as shown in FIG. 1, assuming a conventional horizontally oriented apparatus 10 and a rightward thrust of the ram 14 through the cavity. The redraw sleeve 18 applies a force to a base or bottom portion of a blank. The ram 14 forces the blank through an annular redraw ring 22 to reduce the diameter of the cup and form the metal cup described previously. After the drawing step, the punch 12 maintains the diameter of the cup substantially constant as subsequent tools lengthen the sidewall as described above.
As an aside, the assumed orientation is for purposes of describing the prior art and, later, the invention, and in no way limits the invention to the orientation other than in terms of the relative positioning of the elements of the prior art and the invention.
The redraw ring 22 includes a carbide insert 26 which operatively engages the metal cup. The redraw ring 22 is supported in the apparatus 10 by a housing 28. The housing 28 includes a recess 30 in which the redraw ring 22 is supported in the apparatus 10.
Ironing rings 34 are located axially beyond the redraw ring 22. In the apparatus 10 shown, there are three ironing rings 34. Again, the purpose of the ironing tools 34 is to lengthen and thin the metal in the sidewall of the can body as the blank passes between the ironing tools 34 and the ram 14. Second rings 35 associated with the first two ironing rings 34 and located axially beyond are for guiding the ram 14.
A domer 38 is located at the end of the apparatus 10 after the ironing tools 34. The domer 38 is provided for reshaping the bottom profile of the can body after the sidewall has been fully formed.
One can body defect that is associated with the draw and iron process results in a top edge of the can body sidewall having unequal heights about the circumference of an open end of the can body opposite the reformed bottom end. This can be caused by unequal pressure applied by the redraw sleeve 18 on the metal blank against the redraw ring 22. Machine operators will often shim the apparatus to adjust the clearance between the ram 14 and the tooling 22,34 to counteract the effect of the uneven pressure.
For instance, in an attempt to achieve equal pressure around the blank, the operator will place shims in the tool pack. This can change the angle of the entire tool pack, including not only the redraw sleeve 18 and redraw ring 22, but also the ironing rings 34. The shim is typically placed at position A, as shown in FIG. 1. If the operator determines that there is excessive variation in the top edge of the container body height, he/she would add a shim at position A on FIG. 1 to correctly reposition the redrawing ring 22. However, the operator does not know the thickness of the shim that is needed. Therefore, he/she must use trial and error to determine the correct thickness of the shim.
One of the problems with shimming is that the operators must place them consistently. If there is a jam, the operators have to remove the tooling. When the operator replaces the tooling, he/she is supposed to ensure the can quality is good, and add shims as necessary. Moreover, the shims often do not stay in place and must be reinserted when variability arises. Additionally, shims are stuck to the apparatus using grease, and the shims fall out easily.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior draw and iron can body apparatuses of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.